Threading die



April 28, 1931. JUDGE 1,803,192

' THREADING DIE Filed May 5, 1930 Patented Apr. 28, 1931 UNITED STATES PATENT OFFICE FRANKLIN .J' UDGE, OF GREENFIELD, MASSACHUSETTS, ASSIGNOR TO GREENFIELD TAP & DIE CORPORATION, OF GREENFIELD, MASSACHUSETTS, A CORPORATION OF MASSA- GHUSETTS THREADING DIE Application filed May 5, 1930. Serial No. 449,709.

This invention relates to a threading die of the general type disclosed in the prior patent to Loomer, No. 1,212,971, issued January 16, 1917.

It is the general object of the invention to improve the construction of such threading dies, to the end that they may be more effective in operation and better adapted to their intended purposes.-

To the attainment of this general object, one important feature of the invention relates to the provision of an improved form of cutting element or land by which ample strength is attained and the operation of the die is much improved. My improved construction is particularlv satisfactory in its action during the backing-off of the die, as the wedging of chips in the die is practically eliminated.

My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawings, in which Fig. 1 is a side elevation of my improved threading die;

Figs; 2 and 3 are end views, looking in the diriection of the arrows 2 and 3 in Fig. 11; an

Fig. 4 is an end view of a die having a different number of threading lands.

Referrin to Figs. 1 to 3, I have shown a threading ie comprising an annular ring or base portion 10 with a plurality of prongs or threading lands 11 projecting axially therefrom. The lands 11 are formed with conical outer surfaces, as indicated at 12, to fit within the conical end portion of a suitable holder. not shown. The lands 11 are threaded on their inner faces, as indicated at 14, and the advance or leading side faces 16 are in planes slightly inclined rearward and outward from radial, so that there is a slight hook to the cutting edge.

The exact position of the face 16 varies somewhat in accordance with the diameter of the work and also with the material, as an increased hook effect is desirable for certain kinds of material, while a decreased hook produced better results in other materials.

The rear face of each land is formed with an inner portion 20 substantially in a radial plane and with an outer portion 22 disposed at an oblique and substantial angle thereto. The substantially radial face 20 extends to the roots of the threads 14 or slightly outside thereof.

The provision of this radial face is found to greatly improve the operation of the die when backing the die off of a thread after a threadcutting operation. The radial rear face forms in eifecta second cutting face, which clears the burrs from the thread and aids materially in producing a smooth and well finished piece of work.

Furthermore, the face 20 being substantially radial, there is very little chance of chips being wedged against this face during the baclfing-oif operation, as was the case where the rear face 22 extended to the extreme inner edges of the teeth 14.

In actual commercial operation, the provision of the inner radial face 20 has been found to produce very remarkably improved results.

While the face 20 is made substantially radial for the reasons above stated, the oblique face 22 is placed at as great an angle thereto as is consistent with clearance, in order to increase the cross section of the outer segmental portion as much as possible, thus correspondingly increasing the strength of the die.

The construction in Fig. 4 is similar to that already described but shows a die having three cutting lands, while the die in Figs. 1 to 3 has four cutting lands. It will be understood that the invention is applicable to dies having any number of lands and of any diameter or pitch of thread.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is 1. A threading die comprising an annular portion having a plurality of spaced thread cutting lands projecting therefrom, each land being provided with cutting teeth on its inner face and the rear face of each land being formed with inner and outer portions, the mner tooth portion being substantially in a radial plane and the outer ortion extending at an oblique angle to said inner portion, whereby the cross section of the land is increased.

2. A threading die comprising an annular portion having a plurality of spaced thread cutting lands projected therefrom, each land being provided with cutting teeth on its inner face and the rear face of each land being formed with inner and outer portions, the inner portion extending outwardly slightly beyond the roots of the cutting teeth and substantially in a radial plane and the outer plane portion flaring obliquely rearward from said radial plane to increase the cross section of the land.

In testimony whereof I have hereunto affixed my signature.

FRANKLIN JUDGE. 

